I’ve never been a fan of film’s mumblecore movement or its chief purveyors, Mark and Jay Duplass. The whole idea of twenty-somethings prattling on about their mundane lives in improvised scenes shot with handheld digital cameras makes me cringe. With this in mind, it was with great trepidation that I walked into the Duplasses’ “Cyrus,” the story of a slightly crazed 21-year-old new-age musician who has grown much too close to his mother.

Al Alexander

I’ve never been a fan of film’s mumblecore movement or its chief purveyors, Mark and Jay Duplass. The whole idea of twenty-somethings prattling on about their mundane lives in improvised scenes shot with handheld digital cameras makes me cringe.

I’m not certain, but it’s a good bet that it wasn’t a coincidence that the villain in the brothers’ “Baghead” wore a sack over his noggin. I would have been ashamed, too.

With this in mind, it was with great trepidation that I walked into the Duplasses’ “Cyrus,” the story of a slightly crazed 21-year-old new-age musician who has grown much too close to his mother.

I walked out a changed man. Not only did I learn to admire and respect the Duplass brothers, I also discovered a newfound appreciation for roly-poly Jonah Hill.

OK, I wasn’t buying the notion that the round mound of clown crawled out of Marisa Tomei’s womb (ouch!), but I was digging how gracefully he walked the line between lovable and creepy, never tipping off on which side of the rope he’d end up falling.

Other than Larry David, I cannot remember an actor who had me so on edge, or one who made me feel more wonderfully uncomfortable. I was also a tad envious when the young man strutted into the bathroom and shut the door while Tomei, playing his mom, was buck naked in the shower. Some actors have all the luck.

But I regress. Back to the issue at hand: Marisa Tomei, naked in the shower. Given my love for the gorgeous Oscar winner, that alone is enough reason to like any movie. But the Duplass brothers have gone one better and given her a fairly decent story to go with the gratuitous nudity.

It involves a bizarre love triangle between Hill, Tomei and Mom’s new sad-sack boyfriend, played splendidly by the master of deadpan, John C. Reilly. Thankfully, this ménage à trois is pretty platonic, but it does incorporate intriguing elements of jealousy, ego and comedic one-upmanship.

The dynamic here with the most authority, however, is the insight the Duplass brothers offer into the emotional minefield that results when a relationship between a single mother and her only child grows too insular and codependent for their own good.

It’s a shame Sigmund Freud didn’t live to see it. Luckily, those of us still among the breathing can – and should – see it, for no other reason than the extraordinary performances by the three leads. They flawlessly turn caricatures into full-bodied characters by adding realism and dimension through their extensive improvisational skills.

That proves invaluable, too, because the underlying story is rather preposterous. And I don’t necessarily mean the fantastical conceit that a woman who looks like Tomei would fall for an awkward schlub like Reilly’s John, a divorced loser who still clings to his overly patient ex, played by the great Catherine Keener.

He and Tomei’s Molly meet cute at a party. He’s out back urinating in the bushes and she catches him in the act. Most people, of course, would be repulsed. But not Molly; she inexplicably starts flirting with him.

One thing leads to another, and before you know it, John is stalking the somewhat secretive Molly to find out where she lives and why she is so reluctant to open up to him. And what he finds is Hill’s Cyrus, a man-child musical genius with an ornery streak a mile long.

Condescension, jealousy and distrust quickly ensue. And in literally no time, John and Cyrus find themselves engaged in an intense game of psychological warfare.

It proves as ridiculous as it sounds, too. There is also the inescapable feeling that you’ve seen this sort of thing before. And, you probably have. Reilly alone did two movies two summers ago, “Step Brothers” and “The Promotion,” in which he was a combatant in an exchange of pranks and dirty tricks with a rival.

Despite the familiarity of the story, the Duplasses, with a huge assist from their actors, manage to make it feel just different enough to succeed. And the reason “Cyrus” works as well as it does is because the characters’ motivations – no matter how evil they might seem – are always borne out of love.

You realize that because of the emotional attachment you develop for the characters. Sure, they’re selfish and they behave childishly, but no matter how ill at ease they make you feel, you cannot help but be drawn to them and empathize.

Clearly, it’s not a movie for everyone, but “Cyrus” is sure to appeal to a much larger audience than any of the Duplasses’ previous films. And if, like me, you were among the unfortunate few who saw “Baghead” or their debut, “The Puffy Chair,” you’ll marvel at the exponential jump in talent and maturity on display.

That, along with their stellar cast, make “Cyrus” one of the summer’s edgiest delights. And in a summer as lame as this one, that’s saying a lot.

CYRUS (R for language and some sexual material.) Cast includes Jonah Hill, Marisa Tomei, John C. Reilly and Catherine Keener. Written and directed by Mark and Jay Duplass. 3 stars out of 4.